RDMA/rtrs: Define MIN_CHUNK_SIZE

stable inclusion
from stable-v5.10.137
commit 2b3dcfbece1c2a7dcf69616db7bdab77d0132354
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I60PLB

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2b3dcfbece1c2a7dcf69616db7bdab77d0132354

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[ Upstream commit 3f3d0eab ]

Define MIN_CHUNK_SIZE to replace the hard-coding number.
We need 4k for metadata, so MIN_CHUNK_SIZE should be at least 8k.

Link: https://lore.kernel.org/r/20210528113018.52290-7-jinpu.wang@ionos.com


Signed-off-by: Gioh Kim <gi-oh.kim@ionos.com>
Signed-off-by: Jack Wang <jinpu.wang@ionos.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>
Reviewed-by: Wei Li <liwei391@huawei.com>